Two equivalent ways of drawing a phylogeny

The two phylogenies of the vertebrates shown each illustrate exactly the same information. The phylogeny on the left (A) is sometimes referred to as a tree representation, whereas that on the right (B) is termed a ladder representation. In each, time flows from left to right, so that the branch tips at the right represent current groups, whereas the interior nodes (nodes on the inner section of the tree) represent ancestral populations. For example, the red dot indicates the common ancestor of birds and crocodilians, whereas the blue dot indicates the common ancestor to all tetrapods. The orange line segment is the root of the tree. Adapted from the Center for North American Herpetology (2010).